Lithium niobate modulators for fiber optic communications systems

June, 2003 Veracruz, Mexico Pascal MOLLIER

Lithium Lithium niobate modulators niobate modulators for for fiber fiber optic optic communications communications systemssystems

Dr Pascal MOLLIERCOOPHOTLINE TechnologiesBesançon - France


OutlineOutline

•• Introduction : Introduction : the telecommunication marketthe telecommunication market•• PHOTLINE TechnologiesPHOTLINE Technologies•• Fiber optic Fiber optic communicationscommunications•• Principle Principle of of operationoperation of a lithium of a lithium niobate modulatorniobate modulator•• Fabrication Fabrication technologytechnology•• Main Main characteristics characteristics of an of an intensityintensity LiNbO3 LiNbO3 modulatorsmodulators•• Review Review of of different modulatorsdifferent modulators•• Overwiew Overwiew of of the telecommunication marketthe telecommunication market


Telecommunication market

•• The telecommunications sector is facing increasing The telecommunications sector is facing increasing demand for higher data rates transmitted over optical demand for higher data rates transmitted over optical fiber networksfiber networks

•• The forecast evolution from 10 The forecast evolution from 10 GbGb/s to 40 /s to 40 GbGb/s will /s will occur around 2005occur around 2005--2007 in long haul DWDM networks 2007 in long haul DWDM networks using a new generation of optical components, using a new generation of optical components, electronics systems and subsystems.electronics systems and subsystems.


The actors of the telecommunication market

CustumersCustumers

ProvidersProviders

OperatorsOperators

SystemsSystems

SubSub--systemssystems

ComponentsComponents PHOTLINE TechnologiesPHOTLINE Technologies


PHOTLINE TechnologiesPHOTLINE Technologies

•• A French spinA French spin--off of the CNRS Optics Laboratory at the off of the CNRS Optics Laboratory at the University of University of FrancheFranche--ComtéComté at at BesançonBesançon, a leading, a leadingOptoelectronicsOptoelectronics and integrated optics research center in and integrated optics research center in FranceFrance

•• An advanced R&D enterprise An advanced R&D enterprise designing and developing designing and developing electroelectro--optic chips and devices optic chips and devices based on state based on state ––ofof--thethe--art art lithium lithium niobateniobate technologytechnology


The foundersThe founders

•• PhotlinePhotline was founded in September 2000 by Henri was founded in September 2000 by Henri PORTE PORTE –– CEO, Pascal MOLLIER CEO, Pascal MOLLIER –– COO and COO and JérômeJérômeHAUDEN HAUDEN –– CTO. We are three full time researchers in CTO. We are three full time researchers in optics, electronics and microwave technology, bringing optics, electronics and microwave technology, bringing with them more than ten years active research with them more than ten years active research experience in lithium experience in lithium niobateniobate technology. technology.

•• Our expertise has yielded numerous scientific Our expertise has yielded numerous scientific publications and patentspublications and patents

•• PhotlinePhotline was created in the frame of an incubatorwas created in the frame of an incubator•• The main site is located in a building of the University of The main site is located in a building of the University of

BesançonBesançon..


InvestorsInvestors inin PhotlinePhotline are :are :• ThalesThales Venture,Venture, thethe ventureventure capitalist company from the capitalist company from the

ThalesThales group,group,•• NetTestNetTest, a, a leading providerleading provider of testof test equipment andequipment and test test

solutions forsolutions for telecommunicationtelecommunication networksnetworks•• Alcatel OptronicsAlcatel Optronics (AVANEX), a premier manufacturer of (AVANEX), a premier manufacturer of

activeactive andand passive components forpassive components for the fiber optics the fiber optics telecommunicationtelecommunication. .

•• FIST : FIST : 11-- CNRS : (Centre National de la Recherche CNRS : (Centre National de la Recherche Scientifique) National Scientifique) National CenterCenter forfor Scientific Research is theScientific Research is theFrench public basicFrench public basic--research organizationresearch organization. .

2 2 -- UniversityUniversity of Francheof Franche--Comté (Besançon)Comté (Besançon)


OverviewOverview

•• Founded:Founded: September 2000September 2000

•• Site Locations:Site Locations: BesançonBesançon and and MarcoussisMarcoussis (20 (20 km from Paris), Francekm from Paris), France

•• Employees:Employees: 16 (11 16 (11 BesBes, 5 Mar), 5 Mar)

•• Funding:Funding: ~$2.5M Investment ~$2.5M Investment raised in November 2000raised in November 2000

•• FabFab Completion:Completion: June 2001June 2001


MissionMission•• PHOTLINE Technologies one missionPHOTLINE Technologies one mission isis toto provideprovide toto the the

telecom industry hightelecom industry high--speed modulation solutionsspeed modulation solutions withwithexcellence in performanceexcellence in performance andand maximummaximumvalue forvalue for integrationintegration..


Fiber optic Fiber optic communication communication systemssystems

Basic Basic frame frame in in the the 80’s80’s

Laser + Laser + Optical fiberOptical fiber + + photodiodephotodiode

ElectronicElectronic amplifieramplifier

1990 EDFA = révolution1990 EDFA = révolution

WDM WDM and and DWDMDWDM


WDM (DWDM) long haul and high WDM (DWDM) long haul and high data rates networksdata rates networks


Direct modulation or Direct modulation or externalexternalmodulation ?modulation ?Propagation of anPropagation of an opticaloptical pulsepulse produced produced by aby a switchedswitched gain DFBgain DFB semiconductor semiconductor laser in a dispersive laser in a dispersive

medium medium ((silica optical silica optical

fiberfiber). ). Dispersion Dispersion increases increases thethe pulsepulse widthwidth

Optical spectrumOptical spectrum

Time profilesTime profiles


8

Propagation ofPropagation of the samethe same pulsepulseproducedproduced by anby an externalexternal MZ MZ

modulatormodulator.. When When externally externally modulatedmodulated, , the the pulse pulse width is width is

weakly affectedweakly affected by by dispersiondispersion

Optical spectrumOptical spectrum

Time profilesTime profilesExternalExternal modulation : modulation :

lithiumlithium niobate modulatorsniobate modulators


MachMach--Zehnder optical modulatorZehnder optical modulator•• Lithium Lithium niobateniobate technology is the best solution for the external technology is the best solution for the external

modulation of light at very high data rates.modulation of light at very high data rates.•• It offers ideal tradeoff in terms of low loss, low driving voltaIt offers ideal tradeoff in terms of low loss, low driving voltage, ge,

broad bandwidth and low chirp.broad bandwidth and low chirp.

DC DC ElectrodesElectrodes

RF RF ElectrodesElectrodes


2000

1990

1986

1980

1965

1975

1974

1972

1969

1961

Lithium niobate optical fiber telecommunications

1 st optical fiberElectro-optic properties

semiconductor laser

planar integrated opticprism coupling

P.K.Tien, S.E.Miller,, R.Ulrich, A.Yariv, H.Kogelnik, E.A.J. Marcatili

1st optical fiber transmission(20 dB/km)

optical fiber transmission2dB/km + lasers SC

1st phase modulator Ti:LiNbO3(I.P.Kaminow)

1st directional couplerM.Papuchon (Thomson CSF-LCR)

Epitaxiale growthLiBO3

Commercial high speed modulators(3-18GHz) Crystal Technology,

Pilkington, GEC, BTD)

850 nm multimode opti fiber transmission

1300nm sub-marine transmissi

EDFA

1550 nm transmission systemhigh data rate > 20 Gb/s

long distance 150 - 12000kmSumitomo, IOC, UTP

1950

Integrated optic

The The lithium lithium niobateniobate

(LiNbO(LiNbO33) story) storyo


LiNbO3 LiNbO3 integrated opticsintegrated optics

Main Main advantagesadvantages ::•• LiNbOLiNbO33 is is an an electroptic materialelectroptic material•• Composants compacts.Composants compacts.•• Active components (Active components (modulatorsmodulators…).…).•• LowLow drivingdriving voltage.voltage.•• High High data rate (20 data rate (20 -- 4040 GHzGHz).).•• Good Good compatibility compatibility with optical fiberswith optical fibers•• Pigtailling Pigtailling : : relatively easyrelatively easy ((buttbutt couplingcoupling).).•• Wafer fabrication.Wafer fabrication.•• LigthLigth fabricationfabrication technologytechnology (<5(<5--77 mask layersmask layers).).


The MachThe Mach--Zehnder modulator Zehnder modulator principleprinciple

CW light inputCW light input

CW light inputCW light input

11

00


Half wave Half wave voltage voltage andand extinction ratioextinction ratio

• The half wave voltage is given by : Vπ=λs/n3r33Γlλ is the optical wavelength, s is the electrode gap, n is the optical refractive index, r is the electro-optic coefficient, Γ is the electric-optic overlap coefficient and l is the electrode length.

Typical value between5 and 6 volts

• The optical extinction ratiois given by ε=10log(Pmax/Pmin)Typical value between 25 and 35 dB


Lithium Lithium niobate intensity modulator niobate intensity modulator OpticalOptical chipchip

LiNbO3 Optical chip

DCDC electrodeselectrodes

RFRF electrodeselectrodes

SlaveSlave

Optical fiberOptical fiber


Critical parametersCritical parameters

•• Optical Optical insertion insertion losseslosses..

•• Characteristic impedanceCharacteristic impedance of of the the RF RF electrodes and low electrodes and low driving driving voltage (voltage (VVππ).).

•• Microwave lossesMicrowave losses in CPW RF in CPW RF electrodeselectrodes..

•• Effective Effective microwavemicrowave index.index.

•• ChirpChirp


RefractiveRefractive index profileindex profile obtainedobtained by by thermal diffusion ofthermal diffusion of titaniumtitanium in in

lithiumlithium niobateniobate

-100

10

0

10

20

2.14

2.15

2.16

Opt

ical

O

ptic

al in

dex

inde

x

WidthWidth, µm, µm

DepthDepth, µm, µm


Insertion Insertion losseslossesThe The spatial distribution ofspatial distribution of the optical fieldthe optical field in ain a TiTi:LiNbO3:LiNbO3

waveguide andwaveguide and in anin an optical fiber optical fiber match match very wellvery well

Optical fiberOptical fiberTiTi:LiNbO3 :LiNbO3 waveguidewaveguide

Dep

thD

epth

, µm

, µm

Dep

thD

epth

, µm

, µm

WidthWidth, µm, µm WidthWidth, µm, µm


Characteristic impedance

The characteristic impedance The characteristic impedance dependsdepends onon thethe electrodeelectrode design design structure (CPW structure (CPW coplanarcoplanar wavewaveguide). guide).

It is necessaryIt is necessary toto maintainmaintain aa lowlowvoltagevoltage characteristiccharacteristic i.e. ai.e. a smallsmallgap (s)gap (s)


Microwave lossesMicrowave losses

The microwave lossesThe microwave losses inin the the center conductorcenter conductor come from come from a a skinskin effecteffect;; here the losses here the losses dependsdepends onon thethe squaresquare rootroot ofofthe frequencythe frequency


Effective Effective microwave microwave indexindex

M(f) =M(f) = expexp((--ααl/2)l/2)

aa is the electrode lossesis the electrode losses, , ξξ=(2=(2ππf/c)(nf/c)(nµµ--n) n) is the is the electricelectric--optical mistmatchoptical mistmatch..

The smalThe smal--signalsignal frequency frequency response is givenresponse is given by :by :

[([(sinhsinh((ααl/2)+sinl/2)+sin22((ξξll/2)]/2)]1/21/2

[([(ααl/2)l/2)22+(+(ξξll/2)/2)22]]1/21/2

Traveling wave electrodes with Traveling wave electrodes with velocity matching between optical velocity matching between optical and microwave field and microwave field are are mandatorymandatoryforfor broadband electrobroadband electro--opticopticmodulationmodulation


ChirpChirp•• Chirp represents Chirp represents an an unwantedunwanted phase shift phase shift and and cause light cause light

pulses pulses broadening and hence it limits the broadening and hence it limits the maximum maximum frequency response frequency response of an of an optical linkoptical link..

TheThe phase shift phase shift is related is related to to intensity intensity variation as :variation as :((ddφφ//dtdt)=)=ααcc(1/2I)((1/2I)(dIdI//dtdt))

ααcc is the chirp parameteris the chirp parameter

•• In In the the case of case of external mopdulatorexternal mopdulator, , chirp is generally lower chirp is generally lower thanthan in in directly modulated directly modulated laser.laser.

•• XX--cut cut LiNbO3 LiNbO3 modulators modulators are are theoretically chirp theoretically chirp free free devicesdevices..


Fabrication Fabrication processprocess

PhotlinePhotline masters all stages of development and production of masters all stages of development and production of lithium lithium niobateniobate based modulatorsbased modulators

Using dedicated software for optical and microwave modeling, Using dedicated software for optical and microwave modeling, PhotlinePhotline designs modulators for data rates up to 40 designs modulators for data rates up to 40 GbGb/s/s


•• With its extensive technical With its extensive technical knowledge base and knowledge base and experience in designing experience in designing novel architectures, novel architectures, PhotlinePhotline offers customized offers customized solution for multisolution for multi--functional functional modules and devicesmodules and devices Cost reduction is mandatory to Cost reduction is mandatory to

meet market demand.meet market demand.

PhotlinePhotline is developing innovative is developing innovative solutions in solutions in optoopto--electronic electronic integration and packaging for integration and packaging for deployment in the next generation deployment in the next generation of high speed fiber networksof high speed fiber networks


Lithium Lithium niobate niobate componentscomponents

Phase Phase modulatormodulator Intensity modulatorIntensity modulator

Wavelength filterWavelength filterAcoustoAcousto--optic wavelength filteroptic wavelength filter

DirectionalDirectional//wavelengthwavelengthcouplercoupler

TE/TM modes TE/TM modes converterconverter


•• PhotlinePhotline works in an works in an environment of clean environment of clean rooms for rooms for technological technological development, and is development, and is equipped with all the equipped with all the required laboratories required laboratories for assembly and for assembly and testingtesting

Technological FacilitiesTechnological Facilities


We possess all facilities required for 3”We possess all facilities required for 3”--wafer processing using wafer processing using lithographylithography--based technologiesbased technologies

•• Mask alignerMask aligner•• Thin film deposition by plasma and evaporationThin film deposition by plasma and evaporation•• Thick film platingThick film plating•• Dry and wet etching processesDry and wet etching processes•• Diffusion and thermal annealing furnacesDiffusion and thermal annealing furnaces


•• We have developed a precision optical workshop for dicing and We have developed a precision optical workshop for dicing and polishing of individual chipspolishing of individual chips

•• Dedicated benches are used for single mode fiber Dedicated benches are used for single mode fiber pigtailingpigtailing with both with both standard and polarization maintaining fibersstandard and polarization maintaining fibers

•• We perform in house assembly, packaging and mounting of We perform in house assembly, packaging and mounting of microwave RF connectorsmicrowave RF connectors


We are equipped with a complete range of characterization faciliWe are equipped with a complete range of characterization facilities:ties:•• Surface roughness Surface roughness profilometerprofilometer•• Chip Chip proberprober and microwave network analyzerand microwave network analyzer•• OptoelectronicOptoelectronic test benchtest bench•• Qualification benches for optical modulesQualification benches for optical modules•• Digital transmission network analyzerDigital transmission network analyzer


R&DDevicesCustomizationDesign

R&DTechnologyModelingSimulation

AdministrationFinancialManagement

QualificationClean room

technologyPigtailing Tests &

measurement

marketingSales

PackagingDicing

Polishing

Customized devices

10 Gb/s Modulator

The technical staff consists of researchers, engineers and The technical staff consists of researchers, engineers and technicians in optical design, lithography, thin film processingtechnicians in optical design, lithography, thin film processing, , microwave technology and packagingmicrowave technology and packaging

60% of 60% of Photline’sPhotline’s staff has PhD’s.staff has PhD’s.


Products

Intensity modulators Intensity modulators : CMX: CMX--LN10 MXLN10 MX--LN10 MXLN10 MX--LN40LN40

Phase Phase modulators modulators : MPZ: MPZ--LN10, MPZLN10, MPZ--LN40LN40

Compact Compact modulator modulator driver : CMDdriver : CMD--LN10LN10


CharacteristicsCharacteristics• Lithium Niobate X-Cut technology for long-term bias stability &

low chirp• Mach-Zehnder interferometer waveguide using reliable titanium

in-diffusion process• Designed for high performance (FEC) 0C-192 data rates • Suitable for external modulation in long haul DWDM fiber

systems• Operation wavelength: C & L band • Bias electrode separate from RF input• Option: internal monitoring photodiode for bias control• Option: output polarization maintaining fiber • Options: customized additional functions (VOA, Phase

modulator)


Intensity modulators : package footprint

CMX-LN-10Photline Technologies

A B C D E

A RF - GPO maleB GNDC BIASD PHOTDIODE AnodeE PHOTODIODE Cathode

PIN

OU

T

IN

RFDC

MX-LN10-IPD-PP

Outline diagramDimensions are in millimeters

K-female

GNDGND PD output

Photline Technologie s

CMXCMX--LN10 : LN10 : miniature package miniature package compatible compatible with with 300300--pin MSA pin MSA transceivertransceiver

MXMX--LN10 LN10 andand MXMX--LN40 :LN40 :


Modulation transfert Modulation transfert functionfunctionExperimental Experimental modulation transfert modulation transfert function and function and

measurement measurement of of half wavehalf wave voltage : 5.5 Vvoltage : 5.5 V


SS1111 parameterparameter

S11 S11 parameter at the parameter at the input of a 10 Gb/s input of a 10 Gb/s packaged packaged lithium lithium niobate modulatorniobate modulator..


Microwave electrooptic response

ElectroElectro--optic bandwidth optic bandwidth of a 10 Gb/s lithium of a 10 Gb/s lithium niobate niobate modulatormodulator..


Digital transmission and eye diagram

Back to back Back to back eye diagram at eye diagram at 10 Gb/s 10 Gb/s with with a lithium a lithium niobate modulatorniobate modulator..

Lithium Lithium niobate niobate modulator and GaAs modulator and GaAs driver driver –– PRBS = 2PRBS = 22323--11

Vertical Vertical and and horizontal horizontal eye eye opening opening > 85%> 85%


ElectricalVπ RF INPUT @1MHz @ 1565 nm 5.5V

Vπ DC INPUT @ 1Hz @ 1565 nm 6V

Maximum voltage on DC INPUT ± 20 V

MicrowaveS11 return loss 1GHz –20GHz <-8dB

Electro-optical bandwidth @ -3dB > 10GHz

Max RF input power +28 dBm

Ripple <2dB

OpticalCrystal: Lithium Niobate (LiNbO3) X-Cut, Y-Prop

Waveguide process Titanium

Insertion loss <5.5dB

Optical return loss <-35 dB

Contrast at DC (Pmax/Pmin) >20 dB

Chirp <0.1

Max optical input power +20 dBm

Wavelength dependent loss 1520-1620 nm <1dB

PackagingInput fiber PMF PANDA

Output fiber SMF 28 or PMF PANDA

Input RF connector 50 Ω Wiltron Female K

DC Connector Pin Feed-through

Optical Connector FC/PC or FC/APC

Fiber length 1 meter (typ.)

Package Sizes 100 x 15 x 9 mm3

Termination Impedance Internal

Operation Temperature 10°C-65°C

Characteristics


System application: Transmission in fibre & effect of dispersion

10 Gbps 0 km 25 km

50 km 75 km


Driver ERA Driver SHF Driver Alcatel

Driver comparison at 10 Driver comparison at 10 GbpsGbpsNRZ & RZNRZ & RZ


LN Optical chip

RF electrodesDC electrodes

A global A global and multifunctional and multifunctional solution: solution: thethecompact compact modulator modulator driverdriver

Monitoring photodiode

Driver

Charge resistor


Compact Compact modulator modulator driverdriver

Integration of a LN modulator with a P-HEMT GaAs 26dB

driver amplifier

Eye diagram at 10 Gbps NRZ & RZ


Small Footprint Response of the internal monitoring Photodiode to DC bias modulation

S11 S21 E.O.


HighHigh speed Zspeed Z--CutCut phase phase modulatormodulator

MPZMPZ--LN10 LN10 and and MPZMPZ--LN20LN20S21, phase modulator, 526-25

-60

-55

-50

-45

-40

-35

-30

0 5 10 15 20 25 30 35 40

fréquency (GHz)

S , (

dB)

S21 dB

Moy. mobile sur 5 pér. (S21 dB)


NEW!NEW!High speed Z-Cut MZ modulator with zero-

chirp (proprietary design)Vπ=5V, BW=20GHz, IL=-3,8dB

10 Gbs positive slope. 50kms SMF-28

10 Gbs back-to-back 10 Gbs negative slope 50kms SMF-28


Other Other LiNbOLiNbO33 modulatorsmodulatorsLinear electroLinear electro--optic modulator optic modulator : : CATV or CATV or electric analog sub electric analog sub carrierscarriers

BandBand--pass pass electroelectro--optic optic modulatormodulator


OtherOther LiNbOLiNbO33 modulatorsmodulators

Dual drive Dual drive electroelectro--optic modulatoroptic modulator

SSB transmission SSB transmission using using a single a single side band electroside band electro--optic optic modulator modulator has been has been proposedproposed to to overcome overcome dispersion dispersion limitslimits..


Aimed marketAimed market

•• EquipmentsEquipments for for fiberfiber opticoptic transmission transmission systemssystems, , terrestrialterrestrial andand submarinesubmarine, , metrometro or long or long haulhaul networks networks basedbased on DWDM architectures on DWDM architectures

•• Optical market Optical market in 2006 : 1,25 billion US $in 2006 : 1,25 billion US $•• 50% 50% will be will be LN LN Modulators Modulators •• 20% of progression 20% of progression per year after per year after 20022002•• In 2000: total In 2000: total market market for for optical modulators optical modulators 100000 100000

unitsunits perper yearyear. . Forcast evolutionForcast evolution: 500000 : 500000 aroundaround 20062006


Segments of Segments of the marketthe market

New comers

Other (defence, sensors)

Labs and Universities

Big telecoms companies


•• «« Big Telecom CompaniesBig Telecom Companies »» :: AlcatelAlcatel, Nortel, Lucent, , Nortel, Lucent, CienaCiena,, MarconiMarconi,,SiemensSiemens……(+) (+) high potential, first choice referencehigh potential, first choice reference((--) ) long to penetrate, have already partnerslong to penetrate, have already partners

•• «« Telecom New ComersTelecom New Comers »» : transponders and : transponders and tranceiverstranceivers start upsstart ups……(+)(+) not tight by contract with vendors, not tight by contract with vendors, responsivityresponsivity((--)) will they be there tomorrow ?will they be there tomorrow ?

•• Labs & Universities Labs & Universities (+)(+) higher selling price, can be good referencehigher selling price, can be good reference((--)) one piece businessone piece business

•• Others : defense, sensors, instrumentationOthers : defense, sensors, instrumentation……(+)(+) not telecom (!), higher selling price, less competitionnot telecom (!), higher selling price, less competition((--)) specific needsspecific needs


Main customers: Main customers: equipment manufacturersequipment manufacturers

•Nortel

•Alcatel

•Corvis

•Ciena

•Siemens

•Xtera

•Celion


LiNbO3 LiNbO3 competitorscompetitors•Sumitomo (Japan)•Fujitsu (Japan)•JDS Uniphase•Corning OTI•Codeon (Quantum)•Eospace•Triquint (Agere)•Alenia


CompetitiveCompetitive technologiestechnologiesElectrabsorption modulators: Alcatel, Cyoptics

GaAs & InP MZ modulators:Bookham, U2T

Polymer MZ modulators: Pacific Wave industries


Conclusions•• PhotlinePhotline is sizedis sized for for developmentdevelopment stage stage and smalland small production production

needsneeds•• Sales in 2003: 1.5M€ Sales in 2003: 1.5M€ •• First familyFirst family of of product launchedproduct launched in in marchmarch 2002: MX2002: MX--LNLN--1010•• Second line of Second line of productproduct: compact driver+: compact driver+modulatormodulator

CMDCMD--LNLN--10: 10: launched atlaunched at ECOC 2002ECOC 2002•• 40 40 GbsGbs in 2003in 2003•• High seedHigh seed phase phase modulatormodulator up to 20GHzup to 20GHz•• ForcastForcast: : LowLow voltage voltage and zeroand zero chirpchirp modulatormodulator in 2003in 2003•• Forcast evolutionForcast evolution: : telcordiatelcordia qualification in qualification in midmid--20032003•• Industrialization stepIndustrialization step: 2004 ? : 2004 ? DependDepend on on the market the market

opportunitiesopportunities


Thank youThank you

Pascal MOLLIER, COOPascal MOLLIER, COOSee our web See our web site :site :wwwwww..photlinephotline..comcom

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Lithium niobate modulators for fiber optic communications systems